This invention relates to apparatus including seals.
In linear displacement transducers, especially those employing an optical sensor, it is important to prevent contamination entering the sensor. This can be done by means of a flexible seal which is secured at opposite ends to the two parts that are being displaced relative to one another. This can provide an hermetic seal but this leads to problems because there will be a change in pressure difference across the seal on movement of the two parts relative to one another. If there is any damage to the seal, contamination will be pumped into and out of the transducer by virtue of this pressure difference. This can also be a problem in other applications where it is desired to provide a flexible seal between linearly displaceable, members. Changes in temperature or external pressure can also lead to large pressure differences across the flexible seal which can lead to damage.